The present invention relates to the field of steering control for vehicles and in particular to electronic steering control systems.
In a conventional steer-by-wire system as described in Japanese Kokai Patent Application No. Hei 10[1998]-217988, the steering reaction force correction proportional to the detected road surface reaction force is computed and added to the steering reaction force, so that the condition of the road surface is transmitted to the driver.
However, in the vehicle steering device of the prior art, for example, when the vehicle turns an L-shaped corner so that a quick steering wheel response is required, or a shock from the road surface is transmitted due to a bumpy road surface as the steering wheel is turned back, a transient steering force occurs abruptly, the steering wheel may hinder the turning back of the steering wheel, which is undesirable.
In the vehicle steering device described in Japanese Kokai Patent Application No. Hei 10[1998]-217988, and particularly in the steering force computation unit, on the basis of the detection result of the steering force sensor, a steering force (T) applied to the steering column (steering shaft) is computed. At the same time, a control value (aT) (where a is the coefficient corresponding to the steering force gear ratio) for rotating the steering shaft in the direction of applied steering force (T) is also computed.
The road surface reaction force from the steering reaction force sensor is transmitted to the steering reaction force, for example, when the vehicle turns an L-shaped corner, so that quick return steering is required. If the tire dips due to the rough road surface (holes, etc.), due to the signal from the steering reaction force sensor, quick maneuvering of the steering wheel may be hindered, which is undesirable (see FIG. 7). If the embodiment of the present invention is not applied, this occurs because the steering reaction force is added to track the kickback from the road surface, the steering force rises abruptly, and it becomes difficult for the driver to respond quickly.